module ActiveSupport::Callbacks
Callbacks are code hooks that are run at key points in an object's life cycle. The typical use case is to have a base class define a set of callbacks relevant to the other functionality it supplies, so that subclasses can install callbacks that enhance or modify the base functionality without needing to override or redefine methods of the base class.
Mixing in this module allows you to define the events in the object's
life cycle that will support callbacks (via
ClassMethods.define_callbacks
), set the instance methods,
procs, or callback objects to be called (via
ClassMethods.set_callback
), and run the installed callbacks at
the appropriate times (via run_callbacks
).
Three kinds of callbacks are supported: before callbacks, run before a
certain event; after callbacks, run after the event; and around callbacks,
blocks that surround the event, triggering it when they yield. Callback code can be contained in
instance methods, procs or lambdas, or callback objects that respond to
certain predetermined methods. See ClassMethods.set_callback
for details.
class Record include ActiveSupport::Callbacks define_callbacks :save def save run_callbacks :save do puts "- save" end end end class PersonRecord < Record set_callback :save, :before, :saving_message def saving_message puts "saving..." end set_callback :save, :after do |object| puts "saved" end end person = PersonRecord.new person.save
Output:
saving... - save saved
Constants
- CALLBACK_FILTER_TYPES
Public Instance Methods
Runs the callbacks for the given event.
Calls the before and around callbacks in the order they were set, yields the block (if given one), and then runs the after callbacks in reverse order.
If the callback chain was halted, returns false
. Otherwise
returns the result of the block, nil
if no callbacks have been
set, or true
if callbacks have been set but no block is given.
run_callbacks :save do save end
# File lib/active_support/callbacks.rb, line 89 def run_callbacks(kind, &block) send "_run_#{kind}_callbacks", &block end
Private Instance Methods
# File lib/active_support/callbacks.rb, line 95 def __run_callbacks__(callbacks, &block) if callbacks.empty? yield if block_given? else runner = callbacks.compile e = Filters::Environment.new(self, false, nil, block) runner.call(e).value end end
A hook invoked every time a before callback is halted. This can be overridden in AS::Callback implementors in order to provide better debugging/logging.
# File lib/active_support/callbacks.rb, line 108 def halted_callback_hook(filter) end